Phosphorylation of cotton with inorganic phosphates



United States Patent 3,488,140 PHOSPHORYLATION 0F COTTON WITH INORGANIC PHOSPHATES Dudley M. Gallagher, New Orleans, La., assignor to the United States of America as represented by the Secretary of Agriculture N0 Drawing. Filed Apr. 29, 1965, Ser. No. 452,030 Int. Cl. D06m 1/02, 1/22, 1/24 US. 'Cl. 8116 10 Claims ABSTRACT OF THE DISCLOSURE Antisoiling properties are imparted to cotton cellulose fabrics by reacting them with alkali metal salts of various phosphoric acids to produce cellulose phosphate esters. The ammonium derivatives of the phosphorylated materials are also flame-resistant.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a process for the preparation of cotton phosphate esters. More specifically, this invention relates to the preparation of cotton phosphate esters with alkali metal salts of phosphoric acids. The process consists of a treatment to impart to cotton and to other cellulosic textiles, in yarn, fabric, or garment form, antisoiling characteristics, mainly. Furthermore, the ammonium derivatives of the phosphorylated materials are also flame resistant.

The main object of this invention is to provide a process for imparting antisoiling characteristics to cotton and other cellulosic materials.

A second object of this invention is to provide an efficient method of phosphorylating cotton and other cellulosic materials wherein the desired antisoiling qualities are imparted to the said cellulosic materials while the original strength of the treated material is retained.

A third object of this invention is to provide the added feature of flame retardancy to the cellulosic derivatives of the first and second objects wherein the said flame retardancy is imparted to the treated fabrics by conversion to the ammonium salt.

The phosphorylated cotton and other cellulosic materials resulting from the processes of my invention are characterized by excellent antisoiling properties, and the ammonium derivatives of these are characterized by good antiflaming properties. Either of these features or the combination of features finds use in wearing apparel for adults and for children, in household items, and in commercial institutions; these uses can be in the realm of baby and adult bedding, such as sheets, pillowcases, blankets, spreads, and extend to materials which cannot be cleansed as often, such as rugs, draperies, curtains, tablecovers and cloths, furniture and upholstery materials, and the like. Piece goods have potential application of the process of this invention, specifically in the making of shirts, blouses, coveralls, etc.

Cellulose phosphate and phosphorylating agents for cellulose were reviewed by Reid et al. in vol. 41, page 2828 of the December 1949 Industrial and Engineering Chemistry. Information on the phosphorylation of cellulose is rather meager, was said by these investigators in 1949. The state of the art has not advanced much sirice that year. The textiles produced in phosphorylation have been water soluble in some instances, and in other cases the textiles have been very low in strength. The most successful investigators employed phosphorus oxychloride and pyridine as the phosphorylating agent, but the textiles suffer severely from strength losses, although these are substantially flameand glowproof.

In the preparation of phosphorylated fabrics by the urea-phosphoric acid method, losses are minimized slightly and a certain degree of flame retardancy is imparted to the treated fabrics. The products were generally prepared in an effort to obtain fiameproofing for the treated textiles, and a limited degree of success was noted at an impractical cost level for commercial application.

Now I have discovered that by phosphorylating cotton and other cellulosic textiles, an excellent degree of antisoiling is imparted to the treated textiles without a significant loss in strength. Furthermore, by subsequent conversion of the derived cellulosic esters to their ammonium salts, the added feature of flame retardancy is also imparted to the cotton or other cellulosic materials thus treated.

By the process of my invention which is practical and economical, a far superior textile is produced in that little or no loss of strength is imparted to the treated cellulosic materials, the cost of processing textiles is lower than that of the acceptable prior art processes; and due to the fact that no special equipment is required, it can find commercial acceptance much more readily than any of the prior art processes. Phosphorylation of cotton in this process is accomplished by a pad-cure procedure using essentially neutral, aqueous, alkali-metal phosphate or condensed phosphate salts, and a high breaking strength and tearing strength is retained.

Textiles prepared by the process of my invention have nonsoiling qualities, and show rapid cation exchange with some transition metal salts. An added feature of my invention is the further enhancement of utility when the cellulosic ester derivative produced by process of this invention is further modified upon conversion to the ammonium salt. This is done by acidifying the ester, then converting to the ammonium salt by treating the fabric with about from 5% to 20% aqueous ammonium hydroxide.

The cellulose phosphate esters produced by process of this invention are prepared as follows: The scoured, bleached cotton, or other cellulosic textile is impregnated with a reagent comprising an essentially neutral aqueous alkali-metal phosphate salt solution. The excess solution is removed, the material dried, and then cured. The reagent can be about from 8% to 41.5% by weight. The pH of the solution can be about from 4.0 to 9.7, the less alkaline reactions yielding a higher combined phosphorus content in the finished materialsometimes a weaker finished fabric is obtained in this manner. The temperatures applicable to the impregnating bath are about from 25 to C., and the combined phosphorus content is generally higher at the higher impregnating temperatures. The combined phosphorus content can likewise be made higher by curing the impregnated material at higher temperatures. A preferred wet impregnation (wet pickup) is that about from to or even as high as 136% (see Example 1, below).

Once the fabric has been impregnated to the proper wet pickup, it is generally dried for about from 1 to 10 minutes at about from 180 to 100 C., and cured for about from 1 to 10 minutes at about from to 120 C.

The chemically-modified cottons which I have produced by the process of this invention have been submitted to chemical and physical tests for proper evaluation. The tensile and elongation tests employed were carried out according to ASTM Method D168264, and the tearing strength test according to D192463. In testing the chemically-modified cotton derivatives prepared by process of this invention, the reduced molybdate colorimetric method was'used to analyze for combined phosphorus. A correlation can be made between the phosphorus content and the degree of soiling resistance. The flame resistance of the ammonium derivatives can also be correlated to the phosphorus content. X-ray fluorescence also was used, to verify some of the findings.

Antisoiling qualities were determined by using the technique described below. The phosphorylated samples were soiled by padding an aqueous suspension containing 0.1% Sterling 99-R carbon black, and removing the excess by passing through squeeze rolls, adjusted to maximum pressure. The samples were then dried and subsequently laundered in a standard home-type laundering machine, employing ordinary laundering agents.

The laundered samples were then evaluated for soiling resistance by analyzing for degree of reflectance as measured in a reflectometer. For my purpose, reflectance measurements were made of the treated and the untreated fabric samples before soiling, after soiling, and after laundering.

The treatment of cellulosic materials by the process of this invention is an esterification reaction, which can be described structurally as:

O O Cell-OH NaOl-OH CellOl ONa and Water Na Na wherein CellOH represents cotton or any other cellulosic material.

The fabrics treated by process of this invention which have been determined as acceptable are those which have been phosphorylated to about 1.7% to 3.5% phosphorus content. These have all the qualities sought in the realm of soiling resistance and strength retention. The ammonium derivatives within this range of P content are considered likewise acceptable for their flame resistance with retained strength. The retained strength of the 80 x 80 cotton printcloth which was used in the examples of this specification fall in the realm of about 83% to 93%.

The preferred degree of chemical modification by this process is one which yields a product with at least about 1.5% phosphorus content, since the desired qualities are more evident at this level.

The chemical reagents useful in carrying out the process of this invention are the alkali metal salts of orthophosphates and various condensed phosphates, examples of which are the mixed monoand disodium orthophosphate, sodium hexametaphosphate, sodium tripolyphosphate, tetrasodium pyrophosphate, sodium monohydrogenpyrophosphate, and the like. These and others were used in the course of investigation which led to the present invention. 7 i

The following examples are presented here to illustrate but not to limit the scope of the invention described'in this specification.

EXAMPLE 1 A sample of 80 x 80 cotton printcloth weighing 27.7 grams was impregnated with an aqueous solution 28% by weight of sodium hexametaphosphate at 50 C., passed through a wringer to remove excess solution, and weighed. A 136% wet add-on was obtained, and the wet impregnated material was placed in a vented oven and heated for 1 hour at 150 C, The reacted sample was removed from the oven, a portion cut off and set aside, and the rest of the sample was again placed in the oven and submitted to an additional 1 hour of heat at 160 C., then removed from this environment. Both samples were washed in hot running tap water for about minutes, then allowed to equilibrate at room temperature.

The treated samples were submitted to chemical and physical analyses for evaluation, The phosphorus content of that portion which was set aside after the first heat was 0.72%, while the portipn that had the supplem n ry heat treatment conta ned 1.26%. The break g l 4 strength of these and other samples, together with the proper notations and other data, is presented in tabulated form below. The antisoiling evaluation was obtained by submitting the treated samples together with the proper controls to reflectance measurements, to include values before and after laundering.

The phosphorus analysis was by the reduced molybdate colorimetric method and by X-ray fluorescence. The breaking strength retention determinations were by ASTM-D- 1682-64 Method, and the antisoiling determinations were done by a method described by Beninate, et al., in the American Dyestuif Reporter, vol. 52, No. 20, pp. 2630, Sept. 30. 1963.

EXAMPLE 2 A sample of 80 x 80 cotton printcloth weighing 26.8 grams was impregnated with an aqueous solution 24% by weight of sodium trimetaphosphate at 50 C., passed through a wringer to remove excess solution, and weighed. A 121% wet add-0n was obtained. The wet impregnated material was placed in a vented oven and heated for 1 hour at 150 C., a portion was set aside, and the other portion treated as in Example 1.

The two portions were submitted to the same analyses and evaluation as the portions in Example 1. The two portions of Example 2 were found to contain 1.26% and 1.72% phosphorus, the latter corresponding to the doubly cured portion. Table I shows select data for comparative evaluation.

EXAMPLE 3 A sample of 80 x 80 cotton printcloth weighing 27.5 grams was impregnated with an aqueous solution containing two' salts, specifically 18% by weight of sodium dihydrogen phosphate monohydrate and 19% by weight of disodium hydrogen phosphate, at 70 C., passed through a wringer to remove excess solution, and weighed. A 132% wet add-on was obtained. The wet impregnated material was placed in a vented oven, portioned, and treated exactly as the portions of Example 1.

The two portions were submitted to the same analyses and evaluation as the portions in Example 1. The two portions of Example 3 were found to contain 1.70% and 2.14% phosphorus, the latter corresponding to the doubly cured portion. Table I shows select data for comparative evaluation.

EXAMPLE 4 A sample of 80 x 80 cotton printcloth was placed on a pin-frame (to retain the original dimensions during the treatment) and mercerized with an aqueous 23% sodium hydroxide solution, washed in hot running tap water, and then impregnated with an aqueous solution 27.5%

. by'weight of sodium hexametaphosphate at 70 C., and

allowed to drain in a vertical position for about 10 minutes to remove excess solution. The wet impregnated material'was placed in a vented oven, and heated for 2 minutes at 160" C. and 4 minutes at 160-171 C. The reacted sample was washed in hot running tap water for about 15 2 for comparative evaluation.

minutes, then allowed to equilibrate at room temperature. This sample was submitted to the same analysis and evaluation as the two portions of Example 1. This sample contained 2.75% phosphorus. Table I shows select data EXAMPLE 5 A sample of x 80 cotton printcloth was impregnated with an aq eous solution 7.5% by weight of tetrasodium pyrophosphate at 25 0., passed through a wringer to remove excess solution, and the wet impregnated material was placed in a vented oven and heated 1 hour at 160 C., washed in hot running tap water, and allowed to equilibrate at room temperature.

This sample was submitted to the same analysis and evaluation as the two portions of Example 1. This sample contained 0.26% phosphorus.

EXAMPLE 7 A sample of 80 x 80 cotton printcloth weighing 4.5 grams was impregnated with an aqueous solution 15% by weight of sodium tripolyphosphate (pH 9.7) at 40 C., passed through a wringer to remove excess solution, and the wet impregnated material was placed in a vented oven and heated 1 hour at 160 C., washed in hot running tap water, and allowed to equilibrate at room temperature.

This sample was submitted to the same analysis and evaluation as the two portions of Example 1. This sample contained 1.03% phosphorus.

EXAMPLE 8 A sample of 80 x 80 cotton printcloth weighing 4.6 grams was impregnated with an aqueous solution consisting of 15 grams sodium tripolyphosphate, 78 ml. 1 N HCl, and 20 ml. water (pH 4.5 to 5.0), then placed in a vented oven and heated 30 minutes at 160 C., removed and set aside.

A second sample of the same material weighing 5.9 grams was impregnated with the same solution above, then placed in the same vented oven and heated 60 minutes at the same temperature, and removed from this environment. Both samples were washed with hot running tap water, and allowed to equilibrate at room temperature.

Both of these samples were submitted to the same analysis and evaluation as the two portions of Example 1. The phosphorus content of the first sample was 1.28%, and that of the second sample was 1.59%.

EXAMPLE 9 A sample of 80 x 80 cotton printcloth was impregnated with an aqueous solution consisting of 34.0 grams of potassium monohydrogen phosphate, 47.1 grams of potassium dihydrogen phosphate, and 204 grams of water, then placed in a vented oven and heated 1 hour at 160 C., washed in hot running tap water, and allowed to equilibrate at room temperature.

This sample was submitted to the same analysis and evaluation as the two portions of Example 1. The phosphorus content of the sample of Example 9 was 1.43%.

TABLE I.-PROPERTIES OF PHOSPHORYLATED COTTON FABRICS Reflectance Fabric Samples Percent Example 1 Example 2 (d) Mercerized and applied at temperatures about from 25 to C., said aqueous solutions consisting essentially of about from 8% to 41.5% by weight of an alkalimetal phosphate salt selected from the group consisting of sodium dihydrogenphosphate,

sodium monohydrogenphosphate,

potassium dihydrogenphosphate,

potassium monohydrogenphosphate,

sodium tripolyphosphate,

sodium dihydrogentripolyphosphate,

tetrasodium pyrophosphate,

sodium hexametaphosphate, and

sodium trimetaphosphate;

(b) drying and reacting the wet-impregnated cotton cellulosic textile with the selected alkali-metal phosphate salt for about from 1 to 10 minutes at about from 180 to C.;

(c) curing for about from 1 to 10 minutes at 175 to C.; and

(d) washing and drying the reacted cotton cellulosic textile from (c) to obtain a chemically modified cotton textile derivative containing about from 1.5% to 3.50% phosphorus and having antisoiling characteristics.

2. The process of claim 1 wherein the phosphorus containing alkali metal salt is sodium dihydrogenphosphate.

3. The process of claim 1 wherein the phosphorus containing alkali metal salt is sodium monohydrogenphosphate.

4. The process of claim 1 wherein the phosphorus containing alkali metal salt is potassium dihydrogenphosphate.

5. The process of claim 1 wherein the phosphorus containing alkali metal salt is potassium monohydrogenphosphate.

6. The process of claim 1 wherein the phosphorus containing alkali metal salt is sodium tripolyphosphate.

7. The process of claim 1 wherein the phosphorus containing alkali metal salt is sodium dihydrogentripolyphosphate.

8. The process of claim 1 wherein the phosphorus containing alkali metal salt is tetrasodium pyrophosphate.

9. The process of claim 1 wherein the phosphorus containing alkali metal salt is sodium hexametaphosphate.

10. The process of claim 1 wherein the phosphorus containing alkali metal salt is trimetaphosphate.

References Cited UNITED STATES PATENTS 2,482,756 9/1949 Ford et al. 8-120 2,550,697 5/1951 Kinter et al. 812.0 2,801,242 1/1957 Kerr et al. 812O XR 2,884,413 4/1959 Kerr et al. 8l20 XR 3,104,152. 9/1963 McMackin 81l6 3,243,391 3/1966 Wagner 8116 XR FOREIGN PATENTS 838,394 6/1960 Great Britain.

OTHER REFERENCES Surface Active Agents and Detergents, vol. II, pp. 288296, Schwartz, Perry, and Berch, 1958.

GEORGE E. LESMES, Primary Examiner M. B. WIT TENBERG, Assistant Examiner U.S. Cl. X.R. 8l15.5, 120 

